Two-cylinder viscous liquid pump with pipe switch

ABSTRACT

In a two-cylinder viscous liquid pump with a pipe switch, which by means of a swing pipe alternately connects one of the pump cylinders with the conveyor pipe and releases the other pump cylinder, and which swing pipe is moved along its path of travel by a sliding pin drive via a rocking shaft at varying speeds, powered by one or more hydraulic cylinders, the invention provides a link in the transmission of motion from the drive output to the sliding pin drive, which link serves to change the distance of the connecting element of the sliding pin drive to the axis of the rocking shaft, going from a maximum distance at the beginning and end of the link travel to a minimum distance at the center of the link travel.

The invention concerns a two-cylinder viscous liquid pump. Inparticular, the invention pertains to this type of concrete pump.

The method of operation of such pumps is such that the viscous liquid tobe conveyed is drawn in with the back stroke of one of the pumpcylinders; thus, this cylinder is filled mostly from a so-calledpreliminary feed container. With the forward stroke of the other pumpcylinder, the previously drawn-in viscous liquid is pushed into theconveyor line. It is the function of the pipe switch, at the strokechange, to separate the previously conveying cylinder from the conveyorline and to connect the other pump cylinder, which is filled with thepreviously drawn-in viscous liquid, to the conveyor line. For thispurpose, the swing pipe of the pipe switch travels a swing path in eachof the two possible directions, respectively. The ends of the swing pipeopen with one or the other pump cylinder. Driving the swing pipe bymeans of one or more working cylinders via a sliding pin drive meanspossible the direct transformation of the reciprocating motion of thecylinder piston rods, which serve as the output, via the shuttling swingmotion of the slide into the curved path which is traveled by the swingpipe--which is connected to the sliding pin drive--during its swingingmotion.

According to the invention, the working cylinders operating the slidingpin drive are preferably driven hydraulically and controlled in such away that there results within them an essentially uniform piston speedthrough the power stroke. Since, according to the inventon, the pumpcylinders in the viscous liquid pump, in turn, are preferably driven byhydraulic drive cylinders which can normally be acted upon only when thepipe switch has traveled through its path, the hydraulic workingcylinders of the pipe switch can be switched into a single-circuitsystem of the hydraulic plant and thus be acted upon by the samepressure source which also takes care of the hydraulic drive of the pumpcylinders. However, the invention can also be used with two-circuitsystems, which provide separate pressure sources for driving the swingpipe and the pump. This makes it possible to create the conditions forthe time limitation of switching action of the pipe switch, which on theone hand determine the uniformity of conveying the viscous liquidthrough the conveying line and which, on the other hand, determine theconveying capacity. Of course, these characteristics are determined bythe total interruption of the pumping action between the working strokesof the pump cylinders, and this interruption results not only from theswinging time which the swing pipe requires between the strokes, butalso results, among other things, from the equalization of the shortvolume resulting from the volumetric suction effect, as well as from thereturn-flow of viscous liquid from the conveyor line, which mustlikewise be equalized; however, the return-flow, too, depends on theswinging time.

The return flow of the viscous liquid is due to the fact that the swingpipe is not covering one of the cylinder openings of the pump after theswinging action has begun and the alignment of the swing pipe with theopening of the conveying pump cylinder no longer exists until alignmentwith the pump cylinder which is filled by the suction stroke. This canbe countered mainly by shortening the swinging time of the swing pipe.On the other hand, the geometric proportions of the sliding drive resultin undesired side effects even when the swing pipe speed is onlyrelatively low. This is because the sliding pin drive accelerates theswing pipe, depending on the size of the swinging angle, toward the endof the swinging motion in both directions, if the piston speed of theworking cylinder which drives the swing pipe is kept approximatelyconstant over the swinging range of the swing pipe. The consequence isrough operation of the pipe switch, together with considerable dynamicstresses on its elements and the machine components which interact withthem.

The invention starts with an already known two-cylinder viscous liquidpump (DE-OS No. 32 53 576). Here, an electro-hydraulic control of thepump drive cylinders and the working cylinders of the pipe switch is toassure that the hydraulic pump which generates the pressure has afavorable effect on the time which passes between the end of the pistonmovement in the conveying cylinder until the start of the pumping actionof the other pump cylinder during the swinging movement of the swingpipe; the pump works with varying absorption quantities above zero inthe opposition direction with synchronous operation of the workingcylinder of the swing pipe, which is driven via the main circuit or asecond hydraulic circuit, and the fact that this working cylinder ishydraulically coupled with the working cylinders of the hydraulicpressure generator is meant to make this favorable influence on swingtime possible. Thus, the conveying volume of the hydraulic medium islinearly reduced to zero in the first half of the switching process, andin the second half it is linearly increased in the opposite direction tothe maximum conveying volume. However, in addition to the abovedescribed hydraulic short volumes due to suction, another hydraulicshort volume results in the drive cylinders of the pump cylinders, whichconsiderably increases the pumping interruption time. Generally thisdoes not result in appreciable speed differences of the pistons in theworking cylinders of the swing pipe and of the swing pipe during itspath of travel. Consequently, the harmful dynamic stresses occurringduring the movement of the swing pipe still have to be accepted.

It is the object of the invention, in order to reduce the dynamicstresses and thus to decrease the return flow of the viscous liquid fromthe conveying lines between the ends of the swinging motion, to reducethe residual force of the swing pipe at the ends of the swing path withshort swinging time, thereby improving the degree of uniformity withwhich the viscous fluid is conveyed through the conveying line.

According to the invention the speed of the swinging movement of theswing pipe is maintained positively by means of a non-slip drive,independent of the hydraulic pressurizing of the working cylinder; thisdrive consists at least of the sliding pin drive, the output of theworking cylinders of the swing pipe, and at least one additional linkadded by the invention. In this drive the speed of the swinging movementis continuously changed by changing the distance ratios of A/B overA'/B' in A/B. As opposed to known swing pipes, the swing pipe of theinvention's viscous liquid pump has a multiply increased swinging timein the central portion of the swing path than in the end positions, inwhich the speed can be reduced to a fraction of the average swing pipespeed.

The invention has the advantage that the total switching time of theswing pipe can be kept extremely short, as opposed to comparable swingpipes. As a result of the uneven speed distribution across the swingpath, the swing pipe opening at the pump cylinder end passes the centralposition, which is unfavorable for the return flow of the viscous liquidfrom the conveying line, about twice as fast as usual, for example, sothat consequently the volume of viscous liquid flowing back from theline is reduced to about 1/4. This is due to the squared dependence ofthe path of travel, or the volume, on the time, with constantacceleration of the line content. On the other hand it is possible toreduce the swinging speed at the ends of the swing path to, for example,1/3 of the average speed of the swing pipe speed. Thus the residualforce of the swing pipe is reduced to 1/9 at arrival in the endposition, which results in considerable reduction of stress and wear.Finally, the forces at the swing pipe are inversely proportional to thespeed. Consequently, the forces in the end positions increase to threetimes the average forces number the conditions described above. Thiscorresponds to the practical requirements after safe switching of theswing pipe, which among other things requires the breaking of stoneswhen conveying concrete.

Preferably, when applying the characteristics of the claimed invention,the drive should be designed with the minimum number of drivecomponents.

However, the drive also makes it possible to travel considerableswinging angles, which can be achieved with the characteristics of theembodiment of the invention shown in FIG. 1

Likewise, it is not necessary to use only pivoting components in thedrive. Turning motions over any swinging angle can be achieved with thecharacteristics of the embodiment of the invention shown in FIG. 3.

By using the characteristics of the embodiment of the invention shown inFIG. 2 one can assign a separate working cylinder to each direction ofthe swinging movement.

The characteristics of the embodiments of FIGS. 2, 3, 4, and 5 makepossible a substitution of the sliding guide of the connecting elementsaccording to FIG. 1, or other suitable constructions or alternativeswith varying space conditions.

The details of the invention can be seen in the following descriptionusing several construction examples, which are shown in the drawings.

FIG. 1 is a schematic drawing, i.e. with omission of all details notrequired for an understanding of the invention, of the drive of a swingpipe in a viscous liquid pump according to the invention and as a firstconstruction example,

FIG. 2 corresponding to the presentation in FIG. 1, shows a constructionvariation of the invention in two operative conditions,

FIG. 3 corresponding to the presentations in FIGS. 1 and 2, shows afurther variation of the invention,

FIG. 4 corresponding to the presentation in FIGS. 1 to 3, shows anotherconstruction variation of the invention in two operative conditions,

FIG. 5 corresponding to FIGS. 1 to 4, shows a further constructionexample of the invention, showing a partial presentation of thehydraulic work cycle, and

FIG. 6 is a diagram showing time and swinging path on the abscissa andthe speed of the swinging movements on the ordinate, and giving thecharacteristic curves of known viscous liquid pumps and of theinvention's pump, as well as the mean speed curve.

By means of a sliding pin drive (1) a shaft is driven, the swing axis ofwhich penetrates the drawing plane at 2. Via a rocking lever 3' mountedon the shaft, a swing pipe 4 is switched along an arcuate swing path 5.One of the end positions is shown at 6 in FIG. 1.

The sliding pin drive is connected to a link 3 via a pair of elements.The pair of elements consists of a sleeve 7 and a rod 8, which is guidedin the sleeve, which rod is constructed in one piece with the slidingpin drive. The link 3 is constructed as a ternary gear component and ispermanently mounted on the frame at 10 with a further pair of elements,which form a joint and are located at the opposite end of the link 3,and which are designed as 9. Between the two pairs of elements 7, 8 or9, respectively, is a third pair of elements 11, which is also formed asa joint. This joint serves to connect the piston rod 12 of a hydraulicworking cylinder 13, which is permanently attached to the frame at 15via a joint 14. The piston rod 12 constitutes the output of the driveformed by cylinder 13, via which output the sliding pin drive 1 isdriven.

As shown in FIG. 1, the link 3 is inserted into the kinematic train fromthe output 12 to the sliding pin drive 1. The sliding pin drive 1, shownin its extreme left position, can be moved across the central position(shown partially) into a right end position (not shown), or it can bemoved back from the latter into the left end position. Because of thedesign of the element pair 7, 8 the rod 8 slides continually in thesleeve 7, which is pivoted on the link 3, when the sliding pin drive 1travels through the swing path required to reach the end position of theswing pipe. The effective lever arm of the sliding drive 1 is designedas B and the effective lever arm of the link 3 is designated as A in theend positions of the swing pipe 4, i.e. when the mechanism is in thebent position, as shown in FIG. 1; the effective lever arm of thesliding pin drive 1 is designed at B' and the effective lever arm of thelink 3 is designated as A' in the center position of the swingingmovement, i.e. when the mechanism is in the vertical position as shownin FIG. 1. The lever arm ratio A'/B' amounts to many times, for instance3 to 7 times the corresponding lever arm ratio A/B of the drive. As aresult, the speed of the movement of the swing pipe 4 across the swingpath 6 during the back- and forth movement of the sliding pin drive 1 ischanged continuously. Because of the geometry shown, the swing pipe 4has a greater speed in the central position, which is unfavorable forthe flow-back of the viscous liquid from the conveying line, than at theend of the swing movement. That is to say the speed is reduced at theends of the swing path 6 as opposed to the average speed, which reducesstress and wear.

The construction example according to FIG. 2 is generally unchanged withrespect to the arrangement of the drive, the penetration point 2 of thegeometric axis of the rocking shaft, and the rocking lever 3'. However,the link 3 is located on its own rocking shaft, the geometric axis ofwhich penetrates the geometric axis of the drawing plane at 16. Theshaft is driven by means of a gearwheel or toothed segment 17, whichmoves on a toothed rack 18. The toothed rack connects to each of piston19 and 20, respectively, to which one working cylinder 21 and 22,respectively, has been assigned. The working cylinder 22 moves along themotionless piston rod 23 of the piston 20, which is permanently attachedto the frame at 24. Likewise, the piston rod 25 of the piston 19 ispermanently frame-mounted at 26, so that the working cylinder 21 movesalong the piston rod 25. For the sake of better comprehension, FIG. 2,as well as the following presentations, show the effective lever arms Aof the link 3 and B of the drive pin 1. In the construction example ofFIG. 2 the link 3 is also designed as a drive; it is connected with thejoint 29 of the drive pin 1 by means of a coupling (shown only by a lineat 27 and 28, respectively).

The construction example in FIG. 3 differs from that in FIG. 2 above allby the permanent placement of a double working cylinder 30, which isfixed to the frame at 31. Between the two pistons 32, 33 runs a toothedrack 34 as a connector, which drives the link 3, designed as a drive,via a toothed segment 35; the coupling is shown at 36.

In the construction example in FIG. 4 the drive pin 1, in turn, isconnected to the link 3 via a coupling shown at 37 and 38, respectively.The link 3 is designed as a triangular shift lever. The connecting joint39 of the coupling 37 and 38, respectively, is located in the apex ofthe triangle. One additional connecting joint 40 and 41, respectively,is used to connect the toggle joints 42, 43, which in turn are connectedwith a curved toggle joint 44, and of which joint 43 is permanentlyattached to the frame. In the connecting joint 45 of the toggle joints42 and 44 is located the connection of the output piston rod 12 of thehydraulic working cylinder 13, which forms the drive of the swing pipe 4across the swing path 6.

In the construction example in FIG. 5 two hydraulic drive cylinders 45,46 are used to drive the swing pipe 4 across the swing path 6, whichcylinders are connected with their piston rods 46', 47 to the respectivefree ends of the links 3, which are designed as binary components. Thelinks 3, in turn, are permanently attached to the frame via their otherelement pairs, i.e. joint 48, 49 at 50 and 51. The connection of thelinks 3 with the drive pin 1 is achieved via couplings 52, 53, whichtogether with the binary links 3 form a knuckle joint.

The working cylinders 45, 46 are controlled via a 2/4-way valve 54, ascan be seen from the partial presentation of the hydraulic operatingcircuit. The two hydraulic working cylinders are connected with oneanother via control lines 80, so that when feeding pressure oil P, forexample, to the hydraulic drive cylinder 45, the other hydraulic drivecylinder 46 is acted upon at the piston end via the freelyinterconnected lines a, c and d and drives the drive as far as thecenter position of the swing movement, whereupon a switching, i.e.blocking of the line connection c-d and opening of the line connectiond-c', occurs and the hydraulic working cylinder 45, now acted upon atthe piston end, drives the drive from the central position to the secondend position. With the opposite swing movement, the above-describedcontrol processes are analogously reversed.

I claim:
 1. In a viscous liquid pump having a pair of pumping cylindersand a swing pipe alternately connecting one pumping cylinder with aconveyor pipe and exposing the other pumping cylinder, a drive mechanismfor moving the swing pipe about a pivot point in an arcuate path oftravel at varying speeds along said path, said drive mechanismcomprising:hydraulic motive power means; and linkage means comprising afirst lever extending from the swing pipe and a second lever (3) havingone end pivotally mounted and the other end coupled to said first leverfor applying force to said first lever to move the swing pipe along thearcuate path of travel, said hydraulic motive power means being coupledto said second lever, said linkage means having a first linkage distance(B) extending from the pivot point of the swing pipe to the point offorce application on said first lever and measured normal to thedirection of force application, said linkage means having a secondlinkage distance (A) between said first and second ends of said secondlever and measured normal to the direction of force application, saidlinkage means being formed such that the ratio of the second and firstlinkage distances (A'/B') when said swing pipe is in the center of thearcuate path of travel is greater than the corresponding ratio (A/B)when the swing pipe is at the ends of the path of travel, thereby toprovide greater speed to the swing pipe in the center of the path oftravel than at the ends.
 2. The drive mechanism according to claim 1wherein said one end of said second lever (3) is pivotally mounted at afixed position and wherein said other end of said second lever (3) iscoupled to said first lever by means of a sliding pin drive including asleeve (7) slidable along said first lever (8).
 3. The drive mechanismaccording to claim 1 wherein said second lever (3) is formed as atriangular lever having a first corner (41) pivotally mounted at a fixedlocation, a second corner (40) coupled to said hydraulic motive powermeans, and a third corner (39) connected to said first lever via acoupling bar (37).
 4. The drive mechanism according to claim 1 whereinsaid second lever (3) is mounted to a rotatable shaft so that saidsecond end moves in an arcuate path, said second end of said secondlever being coupled to said first lever by a coupling bar (36); saidhydraulic motive power means being coupled to said shaft for rotatingsame.
 5. The drive mechanism according to claim 1 wherein said secondlever (3) is mounted on a member (17) performing a rolling motionproviding combined linear and rotary movement to said second lever, saidhydraulic motive power means being coupled to said member for providingsaid rolling motion, said second end of said second lever being coupldto said first lever by a coupling bar (27).
 6. The drive mechanismaccording to claim 1 wherein said drive mechanism includes a pair ofsecond levers (3), each of said second levers having one end pivotallymounted at a fixed location and a second end coupled to said first leverby a coupling bar (53, 54), the coupling bars extending in opposingdirections from said first lever, said hydraulic motive power means (45,46) having means coupled to each of said second levers for moving theswing pipe.
 7. The drive mechanism according to claim 6 wherein saidhydraulic motive power means has a pair of hydraulic motors, one of saidmotors being coupled to each of said second levers, said hydraulicmotive power means having hydraulic circuitry interconnecting saidhydraulic motors such that one motor operates said drive mechanism tomove the swing pipe from one end position to a central position and theother hydraulic motor operates said drive mechanism to move the swingpipe from the central position to the other end position.